Implement Symbol.prototype.description (#3995)

The algorithm is based on ECMA-262 v11, 19.4.3.2

Also added a custom dispatcher for the Symbol prototype

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/jerry/es.next/symbol-prototype-description.js

@@ -0,0 +1,75 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+assert(Symbol('desc').description === "desc");
+assert(Symbol.iterator.description === "Symbol.iterator");
+assert(Symbol.for('foo').description === "foo");
+assert(`${Symbol('foo').description}bar` === "foobar");
+
+var desc = Object.getOwnPropertyDescriptor(Symbol.prototype, 'description');
+
+assert(desc.set === undefined);
+assert(typeof desc.get === "function");
+assert(desc.writable === undefined);
+assert(desc.enumerable === false);
+assert(desc.configurable === true);
+
+var sym = Symbol('foo')
+assert(desc.get.call(Object(sym)) === "foo")
+
+var obj_sym = Object(Symbol('foo'));
+assert(obj_sym.description === "foo");
+
+try {
+  desc.get.call(null);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+try {
+  desc.get.call(123);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+try {
+  desc.get.call('test');
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+try {
+  desc.get.call(undefined);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+try {
+  desc.get.call({});
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+try {
+  desc.get.call(new Proxy({}, {}));
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}